Not trying to contradict lutztd but I just did the master cylinder replacement on my 78 240d manual about a month ago. I tried the plain old fashioned top down brake bleeding method that I have used succesfully on many vehicles over many years of being the only one to work on any of my vehicles and it DID NOT work to bleed the clutch slave and master cylinders. I then used the factory method of coupling the right front caliper to the clutch slave cylinder and it worked like a charm. my belief is that air can get trapped in the clutch slave cylinder and master because there is no bleeder on the master cyl. and the slave cyl. bleeder is lower down on the housing unlike calipers and wheel cylinders (on drum brakes) that have their bleeders at the top (where the air naturally wants to go. This, I believe, is why the factory manual says to reverse bleed the system because it forces the air upwards into the brake master cylinder where it naturally wants to go. The most important thing to remember is to keep topping up the brake master cyl. resevoir so that you do not re-introduce air back into the system. Also make sure the bleeders are both clean (maybe someone forgot to put the caps back on them somewhere along the line) or you could be pumping dirt into the system. I know it sounds complicated and somewhat silly to hook up the brake caliper to the clutch slave but it actually is quite easy and works like a charm. Trust me (and mercedes)...

I couldn't find leaking fluid anywhere. The area around the SC looked a little cleaner than the rest of the bottom of the car, but it did not have fresh fluid and there was a coating of dirt on it as well (just not as heavy of a coating as the rest of the car).

To address the "why not use the FSM method" I can respect that question...

the reasons I have not:

1. it seems to me from the description that you need two people to do it (one to open/close bleeder valves while the other pumps breaks). I don't have anyone to help my with this unfortunately.

2. I have seen people saying that it is not any more reliable than other methods. I haven't seen a reason why using the break system to apply pressure on the clutch hydraulic system is any better than using any other method to apply pressure on it to push the fluid and air through.

3. I am a noob and I am trying simpler ways that other people have mentioned because the FSM method seems unnecessarily complicated based on all the reading I have done.

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That is very useful information... thank you.

Do you think there is any reason why using a pressure bleeder to push the fluid through from the bottom would be any worse than using the break system?

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Did you check the calipers at each wheel? If those are ok I am pretty sure I can tell you where the rest of the fluid went.

Regarding the clutch, you almost certainly can bet its the master or slave that is shot.

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1995 E420 Schwarz
1995 E300 Weiss
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#1991 300D Nearly Perfect
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#1995 E320 Touring
#1985 300D Sedan
OBK #42

Like I said, I think air can still "possibly" get trapped in either the clutch master or the salve with a top down bleeding method. Also you do not need to continuously open and close the bleeder like the FSM says. Hook up the clear hose (some of the urethane hose from a local parts store or mortorcycle/small engine shop) to the brake bleeder, open the bleeder and let the fluid fill the hose, plug the hose and open the bleeder on the clutch slave cylinder, then quickly unplug the hose and attach it to the open bleeder on the clutch slave. Go and gently pump the brake pedal while watching the brake master cyl through the windshield. You will see lots of bubbles coming up into the resevoir. when the bubbles stop coming up just stop and go under the car and tighten both bleeders and then remove the hose and you are done.

EDIT: The fluid does not necessarily have to be leaking. as the brake pads and clutch wear the level drops and the clutch pickup is highest on the resevoir so it is the first to suck air and become non op.

Also just realized you were asking about using the pressure bleeder from the bottom. If it is air only then no but if it has its own resevoir then it should work fine just make sure there is plenty of fluid in it.

Its not possible to bleed top down. You are right about pad wear, I assumed he checked the fluid level frequently.

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http://superturbodiesel.com/images/sig.04.10.jpg
1995 E420 Schwarz
1995 E300 Weiss
#1987 300D Sturmmachine
#1991 300D Nearly Perfect
#1994 E320 Cabriolet
#1995 E320 Touring
#1985 300D Sedan
OBK #42

You might also want to bleed the nasty fluid out of the caliper before you pump it into the clutch system, and while you are at it might as well do a complete flush ie: all four calipers. If you get everything squared away and you notice brake fuild loss in short order (with no obvious leaks as you stated) then the most likely scenario is the master cyl. leaking into the booster which it can and will do. Usually there is at least some indication of this (slight dampness around the back of the master cylinder where it bolts to the booster, or a drip out the bottom of the booster where the halves are crimped together) but if it has just started leaking you may not see it immediately. If you see anything like that then it is time for a brake master cyl. rebuild. Do the bleeding first though, it is usually cheaper that way.

Yea, that's right - I am thinking of bleeding bottom up. I have a pressure bleeder and just bought fittings to adapt it to push fluid from the bottom up. My pressure bleeder has a fluid reservoir, so I can push it up through the system. If I don't have to mess with the brake system and risk wasting more fluid and sucking air into the brake system, I will try this first

Only one question before I try it - how in the world do you suck the extra fluid out of the top of the clutch fluid reservoir? If I see it right, the fluid is in a little corner pocket of the reservoir with a plastic "overflow" wall that goes nearly to the top of the reservoir. I don't see how I could fit a turkey baster in there to get it out

edit: duh, nevermind, I can suck it from the brake side and then when it overflows from the clutch's little corner, it will go into the brakes side...

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Ive bled mine 3 times after replacing parts from my original 240D swap because I used the old PNP parts with the method I have described with zero issues, two times from a completely draine system. I started both posts where I described the process I used with the statement this is not the FSM procedure. I have also said repeatedly I tried the bottom up method and couldnt get it to work without fluid just rushing out of the threads of the bleed screw, and many posted it did not work for them for the same reason.. SO could someone who has done the bottom up successfully just post the procedure in detail and please explain to the original poster how to have the bleed screw tight enough not to leak yet still able to pass fluid into the system? Please expand the knowledge base so we all will know the trick to get this to work. Again, Im a shadetree mechanic and I use what works with the limited cash and tool set I have. The FSM suggests a lot of procedures that can be accomplished with out the gold plated MB special tools and I know Im not the only one here who hates to buy a $300 dollar tool to fix something one time. My car is reliable as any here even with the amount of changes I have made with PNP parts.

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1982 300CD Turbo (Otis, "ups & downs") parts for sale
2003 TJ with Hemi (to go anywhere, quickly) sold
2001 Excursion Powerstroke (to go dependably)
1970 Mustang 428SCJ (to go fast)
1962 Corvette LS1 (to go in style)
2001 Schwinn Grape Krate 10spd (if all else fails)

You should not need to introduce much extra fluid. The air will come out first as bubbles and once you see a good stream of fluid swirling around in there with no bubbles then you should be all set. If you want to be extra sure I suppose you could suck a little out of the filler and keep adding new fluid from your pressure bleeder but you will see when you give it a shot.

That is the real advantage of using the brake caliper method, you can watch the brake master cyl. the whole time and you will know for sure when no more air is bubbling up in there. You really should not be afraid of getting air in the caliper. When you crack the bleeders on the calipers the fluid will flow out and will not let any air in if only flowing for a few seconds while you slip the hose over it. The trick with brake bleeders is to just crack it a half turn or so that way fluid only flows out the tip and not out around the threads also which will happen if you loosen them a few turns. So if you have a hose connecting both bleeders which are only cracked just enough to flow it is still a closed system and air cannot get in.

I did just post the proper procedure and it works....All you need is a three foot piece of hose and it can be done all by your lonesome. Trust me I know how to work on my car alone. I have never trusted anyone but myself to work on any of mine.

LutzTD, You are not any cheaper than I am..

but I am talking procedure here... which I figure was specified due to physics... read ' air,liquid,gravity interactions '....

I am usually a one person operation also... but for brake bleeding it just pays to find someone who can help out for 15 minutes.

Always find the bleeder which is farthest from the MC to bleed first...and work back to the one closest to the MC... This varies on cars and is not always the intuitive ' right rear brake...' so actually check the routing of the lines to determine this.

Since the number of turns on the brake bleeders has been mentioned .. which surprises me... let me describe some of the main and important points to brake bleeding.

1. Have verbal signals agreed upon between the person underneath the car and the one pumping.

2. The person pumping initially pumps lightly to see if they have any ' feel' to the pedal. if they do they pump and hold... saying ' pumped ' .... the person on the bleeders ( and it is much cleaner if you have attached rubber lines from the nipple to a glass jar ) opens the bleeder just enough to allow pressurized fluid to squirt out.. AND CLOSES IT IMMEDIATELY... they say " OK" and the pumper can let up on the pedal.

The person pumping gets out of the car and checks the fluid level in the master cylinder because if it is allowed to get too low you have to start all over due to air inclusion.

Then you pump again and hold.... saying 'pumped'
.. and the bleeder repeats the process... only opening the bleeder a slight turn and closing immediately..

At some point the person pumping the brakes should notice a difference in the pedal feel. At the time when no bad looking fluid is still coming out the bleeders, no air is coming out the bleeders and the pedal feels solid they job should be over.

Then be sure the proper amount of fluid exists in the MC.... and close up the hood...

Concerning power bleeders... brake fluid is prone to attracting moisture... which can accumulate and cause steam in certain conditions... so usually when starting a bleeding process it would be with a newly opened can of proper number brake fluid...
If you put a bunch of brake fluid into a power bleeder powered by AIR I would consider that contaminated after the first day/use .

On the other hand, if you evacuated the power bleeder before putting in the new fluid and powered it with NITROGEN... you could probably use it for a long time and several jobs ...

agreed, I have a bug sprayer home made pressure bleeder and I always use fresh DOT4 NAPA fluid and I clean it afterwards, usually I use the whole can by bleeding all of the brakes until its gone rather than throwing away the old fluid, but I never use an opened can beyond the first day. even when younger I have always bled myself, no-one ever seems to push and hold correctly. I used one man bleeders for a long time and pumped the brakes myself, then I graduated to a vacuum bleeder but that always seemed to partially pull air through the threads, then I made the pressure bleeder which eliminates the thread leak issue. I have to do everything myself as my neighbors are "artistic" types and my freinds are miles away. I really did try to bleed the clutch up but even half cracked bleeders leaks for me. Then I tried the method I described, maybe the MB engineers didnt have pressure bleeders. I have no air and my clutch works flawlessly, but from now on I wont post my work arounds. if someone is curious they can PM me.

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1982 300CD Turbo (Otis, "ups & downs") parts for sale
2003 TJ with Hemi (to go anywhere, quickly) sold
2001 Excursion Powerstroke (to go dependably)
1970 Mustang 428SCJ (to go fast)
1962 Corvette LS1 (to go in style)
2001 Schwinn Grape Krate 10spd (if all else fails)

LutzTD, Well, you are certainly following the rules. If everyone did that the world would be a better running place. I never believed in or tried a vacuum bleeder myself.. it does seem that it would pull air through the threads...
Part of the problem is the very very wide range of experience on any forum... people will pick up part of an idea while never having known the whole proper procedure in the original form.. and brakes are SO important....

I just tried bleeding it from the bottom up. I sucked the fluid out of the brake reservoir, then I connected my pressure bleeder (which by the way is a hand pump one with a reservoir) to the bleed valve on the clutch slave cyl. I pumped it up and opened up the bleed valve on the clutch slave cyl.

I had the exact problem lutzTD described of the fluid bleeding out around the threads. I tried various amounts of tightness, but it didn't seem to matter. I had a good amount of brand new fluid in the bleeder, and not very much when I gave up, and only a small amount more up in the brake reservoir, all of which seemed to get there suddenly and then not fill up any more. Something must not have been right. I was trying to do this in the dark. Tomorrow when it is light again I will try to see how much I really need to open the bleed valve to get fluid to flow in but not drip out around the threads.

Would there be any need to pump the clutch pedal during the procedure if using a pressure bleeder pushing from the bottom side?

Thanks you guys, by the way. What you are discussing is helpful to both me and other people who will come to use this forum.

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ok, i will add my 2 cents, i just replaced my clutch pressure plate ect....filled the brake system with fluid, pumped the clutch pedel ten times rapidly, left it alone for 15 min. checked and added fluid and again pumped the clutch another ten times. then cut a stick the proper length to wedge between the drivers seat and the clutch pedel , fully depressing it, got under car and bleed the port on the slave cylinder, repet three times and check fluid levels as you go. i have had a small leak on my brake booster for 5 years and i just refill as needed, new clutch works fine........FWIW Bill

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Gretchen 1981 240D 4-spd 213,000 mi
1979 240D 4-spd 298,000 mi parts car

1994 BMW 325is
1991 Dodge turbo diesel
1997 ford expedition

BILL